Method of and means for the measurement of colors



June 9, 1925.

E. EBlE A METHOD OF AND MEANS FOR THE MEASUREMENT OF COLORS Filed Sept. 1, 1921 Patented June 9, 1925. i

um'rsos'rATEs nnwoon nsinor BERLIN, nnwnarsrsnrnn, ASSIGNQR'TO enown oomrnuinor TE T '0FFI1CE".

BERLIN, NEWHAMPSHIR-E, A ooaronn'rron' or MAINE.

mnrnon or Ann Means FOR THE MEASUREMEN'IOF 'ooLons.

Application filed September 1, 1921. Serial in! 497,588.

vide a method and means by which one may measure the color of bleached pulp, paper or other materials, andclassify such materials according to their color value, and hence toenable one to specify in advance hand .with exactness the standard to which the material must conform. Bleached pulp,

for example, varies considerably in tint, and

the measurement of the extent to which any given batch varies from white is, of commercial importance and has proven a source of difliculty to producers and users of. pulp. Probably the most widely used method .is

. that described in Paper, Vol. XIX,pp. 18, 19 (1916), in which discs of the'pulp are matched with a series of. arbitrary color standards, consisting of rotarylwheels covered or faced with plaster' tinted to various shades lof llight yellow by a soluble material,+potassiuin-chromate. A disc of pulp is secured to each of the standard wheels, and the whole series being rotated at, a speed high enough to eliminate, the effect of surface irregularities, the whole set is viewed at once under constant conditions of illumination. The standard wheels are given arbitrary numbers, accordingto the shade ofyellow, and the pulp is given the number of the color wheel which it matches or most nearly matches.

There are several ,difliculties attendant upon or inherent to this method, which diminish its usefulness or value. Probably the most serious of theseis due to the use of the soluble coloring matter, as a result of Which, while the plaster is setting, varying amounts ofthe potassium chromaterise to the surface, due to. capillary action and evaporation, giving a non-uniformly colored face to the wheel." Moreover, since the faces of the wheels become discolored in use, rendering it necessary from. time to time to turn them down or .reface them with an appropriate tool suchas a chisel, the chromate which is segregated at the surface is re? moved, and the wheel grows gradually white incolon Again, it is diificult to reproduce with exactness as to color the standard wheels,"rendering the standardizw tion uncertain and frequently inaccui'rate.

These d fiicultles. are met in the present process bythe employment of an insoluble reproduciblepigment in lieu of a soluble color-111g matter such as potasfiunrchromate, and the selection of such pigments which donot change theircolor on' prolonged exposure to light and air. Infladdition,and according "to another feature of my invention, instead of forming the entire faces of the .color wheels of a mixtureof plaster and pigment in d-ifi'erent proportions sojas to present Cllllfilfillh'llUGSOI tints, the

of a single mixture inpredetermined pro portions off-plaster or other suitable bodyand pigment, of a predetermined color. In thiscase, the wheels are snrfacedfto produce sectors which vary in color, as fore iample white and yellow, and the color effect of the different wheel's (whenrotating) is varied by vary'lng'the relative areas of the sectors.

Thus a color wheel may have a large sector orlield of pure white plaster, and a small sector of the plaster-pigment mixture, and present, when in rotation, a slightly yellowish color. By decreasingthe white area and increasing the yellow area, the effect produced, when "the wheel is in rotation, is of a deeper yellowish color. colored sector, therefore, determines V the final color effect-produced, and'consequently the numbers or color values. may bev standardized according to the areas of the colored sectors.

' 3 It is also possibleto vary the'color effect "by employmgsectors of different colors. For-examplato g vea grayish tone or hue,

one sector may be black, another yellow and a third white; or, if desired, there may be may thus be selected according to the numbers and sizes or areas o-tthe sectors of different colors. In all the wheels the corresponding sectors,(whetherv blue, black,- yellow' or the like areidentical in color, and vary only as to area. This is of markedimportance, for, having ascertained the exact proportions in which the plaster and pigment aremiXed, the same technique may be "followed thereafter with precisely the same results as to the colorof the mixture.

desired color eitect is produced by the use The area of the 'a'blue or a'red sector, Arbitrary standards loo lit)

For the puiposeot illustrating an app'aratus which may be employed in "carrying out my method, reference may be had to the accompanying drawings in "which,

Figure 1 shows 'in front View a' m'achine having a series of color wheels arranged to be driven simultaneously.

Figure 2 shows a plan View of a portion of the same. i

Figure 3 represents a transverse section V on the line 33 of Figure 1.

Figure t shows one smaller sc'alethe machine in tront elevation and illustrates different types of color wheels which 'inay be employed. 7 V I Figures 5 and 6 illustrate'the method of forming the colored sectors in or on the wheels. r 7

Of course it will be understood that any suitable apparatus maybe 'ei'nployed in lieu of that shown inthe drawings, and hereinafter describechas all that isnecessary is oneor more wheels and means for efiecting its or their rotation. The'illustrated'mm chine, which per se substantially identical, except as'to the formation of the faces of the wheels, with that recommended by the committee on sulphite pulp of the-Technical Association otthe Pulp and "Paper Industry, as set forth in the publication hereinbetore referred to, is eminently satisfactory for the purpose. Briefly, it consists of a't'rame, on which is located "an electric motor lO,'wliichiby a'belt or'cord drives a series of horizontally arranged shafts l l through the medium of pulleys 1'2 thereon. The shafts are fjournaled in suitable bearings 13, '14, and on the front end of each there is pinned 'a wheel "lo'wliieh'm'ay "be in the form ot'a disc with an under-cut an nular groove 16in its face. In thebottoln of the groove are recesses or sockets 17. On the end or each shaft, a knurled knob 18 is screwed, by which a disc '19 of paper or pulp maybe clamped against the central portion otthe wheel. Heretotore the wheels have had the grooves filled with colored plaster, each wheel however presenting a face of unvaryingfcolor or'tint eXcep't 'asit might be imperfect due to segregation'ot' the soluble "pigment in the'v'arying blotches in the face thereof. In such case, discs cut trom'the same sheet 01 paper oij'puip were secured to the, several wheels, which were all rotated at high speed, so that a comparison could be effected-between each pulp disc and its supporting wheel to seeit the pulp mate iedi'n color any one ot'the discs. 7 As previously stated, "I do not employsoluble potassiumchromate. On the contrai y, to obviate the'difficulties herein're rr'ed'to due "to the use 'otfsolubl e coloring matter, I employ an insoluble non-fading pig'n'iei'it. Also, instead of employing commerciallpl'astor of Paris, which varies widely in color,

and thus also introduces "an element of uncertainty in securmg the deslred color or tint in the wheel, 1 preferably employ chem- 0001 the solution to 20 C. and add a solu tion of sulphuric acid made by pouring 19:2 0. c. of concentrated acid to 1 liter of cold distilledwater and cooling to 20 C. Allow to stand at 20 C. for an hour or two, then filter on a Buclmer funnel and wash "tree ot The temperature acid with distilled water. of precipitation is important to insure the proper waterot' crystallization in the finished plaster. The 'precipitateis driedover inight'(1617 hours) at65 C. After drymg it Is broken to .pass through a ten-mesh sieve, placed 1n an evaporating dish and calcined at 110 6. over night (16-17 hours). The calcinedpla'steris then allowed to stand exposed to the atmosphere for about eight hours,when 1t Wlll be found to have taken up water until the total water content is,

between and 9%. The finished plaster ls 'soft and does not require grinding.

Of course, the foregoing procedure need 'notfbe followed but it is given as one method of producing a pure white plaster which maybe used either "alone or when colored with a pigment.

The plaster, inany event, may be hardened by the use of acolorless water soluble colloid, which does not darien on exposure -to air'and light such as. a" gum arabi'c solution' (eg. solution, "distilledlwateifi, which may be employed instead 'otwater alone in preparing the plaster for setting. For the 'plgmentation of the plaster to produce ditlerentfcolors, I may employ i'eproducible non-fading pigments such, tor

example, asilainp black for black sectors, 'ZIHC chrom'ateior yellow sectors, nickel dimethyl glyoxi ne for the red sectors, and Prussian blue for the blue sectors. pigments for producing the same 'or other Other colors may 'be 'used, as desired. In any "event, it is desirable and essential for the best results through along period of time that the permanence of the pigment should persist or remain 'unvarying when exposed to 'hghtand air, that the pigmentshould be capable of'fine subdivision, that the'con- 'ditions ,dfits preparationshould he'c'apable of being stated with sufficient accuracy] that one can 'reproduce it with confidence that its hue and saturation Wlll be unvarying, I

and that differences in the covering POWQL of the IpigmentK'due to variations in the coarseness "or fineness of the particles when comminuted) ma'y be eliminated.

To produce a suitable yellow "pigment, one may proceed as Etollows:Dissolve hours.

grams of G. P. zinc chloride in 1400 cc. of

distilled water'and bring to boiling. Add Concentrated sulphuric acid slowly,-drop by drop, until the precipitated zinchydroxide is just dissolved. (Care must be taken not to add an excess of'acid because thecolorof the zinc chromate precipitated depends,

on the concentration of ammonium hydroxide added later.) While boiling, add a boiling solution of 20 grams potassium chromate dissolved in 600 c. c.-of water;- Continue boiling for a minute or two. Then remove from the heater and while stirring vigorously add 36 c. c. of concentrated ammoniumhydroxide (28%-29% N'H from a burette, slowly (5 c. 0. per minute). Allow to settle and filter on a Buchner funnel. ash with boiling. distilled water until washwater is colorless or very nearly so. Dry at llOVCL; for several If washing is. :not complete, the dried precipitate will have spots of deep reddishyellow. These can be removed by additional iwashing The red nickel dimethyl glyoxime may be precipitated from a slightly ammoniacal solution of a nickel salt by means of an alcohol solution of dimethyl glyoxime. In making the bluesectors, the Prussian blue andcalcium sulphate maybe precipitated from the same solution at the same time by mixing solutions of calcium chloride, a soluble sulphate, a soluble ferrocyanide.

lVhile red nickel dimethyl glyoxime is not strictly an inorganic pigment as are the others herein referred to, yet, like them, it is insoluble .in the liquid vehicle" and possesses the desired permanence of hue and fineness of grain.

In mixing the plaster and the pigment,

care shouldbe exercised to effect a thorough and physically homogeneous mixture. For

the yellow sectors, one may grind 20 parts of the yellow pigment'and 80 parts of plaster until the mixture does not change on further grinding. Preferably it should be capable of passing through a 100-mesh sieve.

The proportions of the pigment and plaster may, of course, be varied,'but, 'onc'e having determined a standard mixture, it

' should not be changed thereafter.

Assuming that a wheel is to have both white and yellow sectors, the area to be covered by each is carefully marked on'the.

wheel. The white or the colored plaster is mixed in a thin putty-like consistency with the gum arabic solutionand applied to the proper part of the wheel,in thefacial groove thereof, as shown in Figure 5, and those portions which project beyond the radial lines bounding the sector may be out after the plaster has set. Usually the white plaster is first applied, and then the colored ferric chloride, and

plaster is applied. I Preferably the thickness of the plaster layers shouldbe sufficient,

by means of a suitable tool. Of course, after the sectors are filled, the plaster must be dried,and this may be done at a tem perature of about, C. for four to five hours. i i Y I find it desirable to moisten the surface of therwheel, after it has'been smoothly, faced on a lathe,'and the dust removed, with distilled water to bind, the loose particles and to form a film of gum over the surface; The colored portion is formed or divided'into a plurality of sectors, which are spaced equi-distant aboutthecenter, so that the speed of rotationlof the disks, to prevent flickering, may be relatively low; Thus, instead of one sector of relatively large area, I may-form two or more sectors which total the same in area. i

The wheels of a given series areall. different, so as to enable one to match agiven sheet of pulp or paper with one oflthem.

As indicating how the Wheelsof a series may vary, and a standardization may be ,to permit the wheel to be faced on a lathe aifected according to the color value, one,

may have" a series as -fOllOWSZ' Y NVhitc Yellow Black Value o wheg sector sector sector Degrees Degrees Degrees 100 320 40 "0 300 55 5 280 70 10 p 260 15 240 20 .220 25 From the foregoing, it is apparent that a standardization of the color values is easily efieoted, and this having once been effected, the color wheels may be reproduced with certainty as to their, line or color value.

vWhat I claim is 1-. Mechanism for gaging color values,

ill)

comprising a series of rotary memberseach areas of one on more colors, the first-mentioned areas gradually varying n size in said series and the colorsbeing nonfading,

nonvariable and reproducible.

3. Mechanism for gaging color values,

comprising a series of rotary members hav- 1ng opaque white and colored sectors, the

white sectors being formed of plaster of Paris and gradually diminishing in area progressively in the series and the colored sectors being formed of homogeneous mixture of plaster of Paris and a n-onfading in soluble pigment and gradually and correspondingly increasing in area in the series. 4i. Mechanism for gaging color values, comprising a series of rotary members each having a plaster face of appreciable thickness, colored with an insoluble invariable reproducible nonfading pigment in homogeneous mixture with said plaster face.

5. A color wheel having a layer of plaster of Paris mixed with an insoluble nonfading finely-divided pigment of an invariable reproducible color.

6. A color wheel having a layer of plaster of Paris mixed with an insoluble nonfading finely-divided pigment invariable and reproducible in color, and hardened with a colorless water-soluble colloid which does not darken on exposure to light and air.

7. A color wheel having a layer of plaster of Paris mixed with an insoluble non tading finely-divided pigment of an invariable reproducible color, and hardened with gum arabic. Y a p 8. Mechanism for gaging color values, comprising a series of rotary members each having sectors consisting of layers of plaster of Paris, one or more of each of such sectors being colored by an insoluble reproducible nonfading pigment mixed with the plaster.

A 9. Mechanism for gaging color values, con prising a series of rotary members each,

faced with a layer of plaster of Paris, said members having sectors, which gradually increase in area in the series, in which zinc chromate is in homogenous admixture with the plaster to impart the same color to all of said sector s. I

10. -Mechanism for gaging col'or values, comprising a series of rotary members each faced with a layer of plaster of Paris, said members having colored sectors, which gradually increase in area in the series, in which a reproducible non'fa'ding insoluble pigment of an invariable color is in homogeneous admixture with the plaster to impart the same color to all of said sectors, said sectors contra sting in color to other sectors of said members, which diminish in area in said series. A

11. Mechanism for gaging color values, comprising a series of rotary members, faced with plaster in a layer ofappreciable thickness, said members having the faei-ngs divided into white sectors and sectors colored by a water-insoluble nonfading pigment in homogeneous admixture with said plaster, said colored sectors gradually increasing in area in the series and the white sectors gradually and correspondingly diminishing in area 1n the sectors.

In testimony whereof I have aflixed my signature.

- Y ELlVOOD EBIE. 

